docs: def save(self, *args, **kwargs):
          """ Saves the topic instance. """
          # It is vital to track the changes of the forum associated with a topic in order to
          # maintain counters up-to-date.
          old_instance = None
          if self.pk:
              old_instance = self.__class__._default_manager.get(pk=self.pk)
  
          # Update the slug field
          self.slug = slugify(force_text(self.subject), allow_unicode=True)
  
          # Do the save
          super().save(*args, **kwargs)
  
          # If any change has been made to the parent forum, trigger the update of the counters
          if old_instance and old_instance.forum != self.forum:
              self.update_trackers()
              # The previous parent forum counters should also be updated
              if old_instance.forum:
                  old_forum = old_instance.forum
                  old_forum.refresh_from_db()
                  old_forum.update_trackers()